THE HERRING AND ITS ALLIES. 393 
four-fifths of the whole number of factories were included. In 1880 the 
number of persons employed in the entire industry was placed at 3,635, 
the amount of capital invested, $2,362,841, the value of products, $2,116,- 
787, including 2,066,396 gallons of oil, worth $733,424, and 68,904 tons 
of guano, worth $1,301,217. The refuse of the oil factories supplies a 
material of much value for manures. As a base for nitrogen it enters 
largely into the composition of most of the manufactured fertilizers. 
THE ALEWIFE, 
The commercial representatives of the Herring in America are perhaps 
the River Herrings and the Shad, which ascend our streams in the spring, 
and, fresh, pickled and smoked, enter very largely into the food resources 
of the Atlantic region. 
Early writers on American fishes, especially Mitchill and De Kay, seem 
to have experienced great difficulty in differentiating into species the vari- 
ous forms of River Herrings or Alewives in our waters. These early 
writers were, however, apparently more discriminating than some of their 
successors, for they recognized differences which have been ignored by 
subsequent writers. They were as much at fault, however, in making too 
many species, as were Storer and Gill in uniting all the forms under one 
specific name. 
The attention of the zoologists of the Fish Commission was first called 
to the probable existence of two species by the persistent opinions of the 
fishermen of the Potomac, who recognized two forms—differing in habit 
and in general appearance—which they called the ‘‘ Branch Herring’’ 
and the ‘‘ Glut Herring ’’ respectively. 
The announcement of the discovery of the two species and a definition 
